Poor performance cold and better warm may indicate an EGR problem.
-Check all the vacuum lines and wiring to the EGR solenoid, EGR valve, and DPFE.
-The two exhaust sensing lines leading to the DPFE can get very brittle and degraded due to the extreme conditions and sometimes need to be replaced.
-You can also clean the EGR passages in the throttle body if you haven't done that already.
Have you checked your OBDII codes if the CEL is on?
IMRC secondary valves pinned open will definitely cause the problem you describe. The engine is expecting MUCH less volume and much higher velocity of intake charge at low RPMs. This is classic IMRC failure.
You need to find yourself a good working IMRC actuator and get those things connected.
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